Patent Literature 1 discloses a carboxylic acid complex composed of benzoic acid, a metal, and an organic ligand which can coordinate with the metal by bidentate coordination, and also discloses that the complex is useful as a methane gas-absorbing material. Non-patent Literatures 1 and 2 disclose a single crystal of one-dimensionally linked organic metal complex composed of benzoic acid, rhodium (Non-patent Literature 1) or copper (Non-patent Literature 2), and pyrazine, and also disclose that the crystal structure of the metal complex changes when the metal complex adsorbs or desorbs carbon dioxide molecules which are guest molecules.
On the other hand, as an adsorbent of vapors of organic solvents such as benzene and toluene, active carbon, zeolite and the like are conventionally used (Patent Literatures 2 and 3). As a hydrogen-absorbing material, alloys and sintered bodies thereof have been used (Patent Literatures 4 and 5).    Patent Literature 1: JP 2000-309592 A    Patent Literature 2: JP 2004-255336 A    Patent Literature 3: JP 2004-261780 A    Patent Literature 4: JP 2003-1389 A    Patent Literature 5: JP 2003-3203 A    Non-patent Literature 1: Satoshi Takamizawa et al., Angew. Chem. Int. Ed. 2003, 42, 4331-4334    Non-patent Literature 1: Satoshi Takamizawa et al., Inorganic Chemistry Communications, Volume 6, Issue 10, October 2003, pp. 1326-1328